Multilayer white printing with white-balance

ABSTRACT

White-balance is improved when printing on colored media, while minimizing the time and use of costly materials required by present approaches. In an embodiment, the typical solid white fill or background layer is altered by including in the white layer one or more of the other colors already available in the printer to shade this layer. Thus, a small amount of cyan, for example, helps balance a pink-ish (red) media; yellow is used for blue media; and magenta is used for green media; as well as combinations thereof. A combination of transparent process inks and opaque white helps to maintain brightness (luminosity).

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to printing. More particularly, the inventionrelates to multilayer printing with white-balance.

2. Description of the Background Art

In photography and image processing, color balance is the globaladjustment of the intensities of the colors, typically red, green, andblue primary colors. An important goal of this adjustment is to renderspecific colors, particularly neutral colors, correctly; hence, thegeneral method is sometimes called gray balance, neutral balance, orwhite balance. Color balance changes the overall mixture of colors in animage and is used for color correction; generalized versions of colorbalance are used to get colors other than neutrals to also appearcorrect or pleasing.

Image data acquired by sensors, either film or electronic image sensors,must be transformed from the acquired values to new values that areappropriate for color reproduction or display. Several aspects of theacquisition and display process make such color correction essential,including the fact that the acquisition sensors do not match the sensorsin the human eye, that the properties of the display medium must beaccounted for, and that the ambient viewing conditions of theacquisition differ from the display viewing conditions.

The color balance operations in popular image editing applicationsusually operate directly on the red, green, and blue channel pixelvalues, without respect to any color sensing or reproduction model. Inshooting film, color balance is typically achieved by using colorcorrection filters over the lights or on the camera lens.

Sometimes the adjustment to keep neutrals neutral is called whitebalance, and the phrase color balance refers to the adjustment that inaddition makes other colors in a displayed image appear to have the samegeneral appearance as the colors in an original scene. It isparticularly important that neutral, i.e. gray, achromatic, and white,colors in a scene appear neutral in the reproduction. Hence, the specialcase of balancing the neutral colors, sometimes gray balance, neutralbalance, or white balance, is a particularly important, perhapsdominant, element of color balancing.

A particular problem occurs when an image is to be printed on a coloredor off-white substrate. In such cases, the image can take on distinctcolor cast. In the art, the influence of an off-white or coloredsubstrate is countered by first printing a layer of white ink on thesubstrate, thus establishing a neutral base upon which the image can beformed. For example, Vutek PressVu, QS, GS, and HS printers all have theability to print multiple layers onto colored media, first printing onewhite layer for a consistent background and then printing other layersfor the standard CMYK (cmykW) image. These printers rely on the whiteink's pigment and opacity to deliver a solid and consistent white baseon which a profiled colored image can be printed.

When printing on strongly colored media, the white ink alone may nothave sufficient opacity without being printed in large, costlyquantities. For example, when printing on a strong red sheet a singlelayer of white may appear to have a slightly pink hue. Adding a secondlayer of white may cure this problem, but at the cost of throughput andink.

An alternative, but unsatisfactory, solution to this problem istime-consuming re-profiling for strongly colored media and avoidingsolid white areas.

It would be advantageous to improve white-balance when printing oncolored media, while minimizing the time and use of costly materialsrequired by present approaches.

SUMMARY OF THE INVENTION

Embodiments of the invention improve white-balance when printing oncolored media, while minimizing the time and use of costly materialsrequired by present approaches. In an embodiment, the typical solidwhite fill or background layer is altered by including in the whitelayer one or more of the other colors already available in the printerto shade this layer. Thus, a small amount of cyan, for example, helpsbalance a pink-ish (red) media; yellow is used for blue media; andmagenta is used for green media; as well as combinations thereof. Acombination of transparent process inks and opaque white helps tomaintain brightness (luminosity).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram that shows at a high level how a printer may bewhite balanced when printing an image on a colored medium according toan embodiment of the invention;

FIG. 2 is a flow diagram that shows how to create a white balanceprofile for a particular ink type, according to an embodiment of theinvention;

FIG. 3 is an example white balance profile associating a proportion of aCMY color with the corresponding measured RGB values of the printed CMYcolor, according to an embodiment of the invention;

FIG. 4 is an example white balance profile associating desired CMYcolors with a percentage of the corresponding CMY color that causes theprinter to create the desired color, according to an embodiment of theinvention;

FIG. 5 illustrates a color wheel showing the inverse colors, accordingto an embodiment of the invention;

FIG. 6 is a flow diagram that shows how to automatically configure aprinter for white balancing using a background layer of white on acolored medium, according to an embodiment of the invention;

FIG. 7 is a flow diagram that shows how to manually configure a printerfor white balancing a background layer of white on a colored medium,according to an embodiment of the invention;

FIG. 8 shows a user interface with which white balance can be adjustedwhen printing an image on a colored medium according to an embodiment ofthe invention;

FIG. 9 is a flow diagram that shows how to print an image on a coloredmedium, according to an embodiment of the invention; and

FIG. 10 is a block schematic diagram that depicts a machine in theexemplary form of a computer system within which a set of instructionsfor causing the machine to perform any of the herein disclosedmethodologies may be executed.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention improve white-balance when printing oncolored media, while minimizing the time and use of costly materialsrequired by present approaches. In an embodiment, the typical solidwhite fill or background layer is altered by including in the whitelayer one or more of the other colors already available in the printerto shade this layer. Thus, a small amount of cyan, for example, helpsbalance a pink-ish (red) media; yellow is used for blue media; andmagenta is used for green media; as well as combinations thereof. Acombination of transparent process inks and opaque white helps tomaintain brightness (luminosity).

FIG. 1 is a flow diagram that shows at a high level how a printer may bewhite balanced when printing an image on a colored medium according tothe invention. In an embodiment of the invention, a white balanceprofile is determined for the specific type of ink installed in theprinter. Different ink types may have different white balance profiles(Step 300). In an embodiment, the printer manufacturer may create one ormore white balance profiles and install them in a printer memory device.In Step 301, an offset color is determined for a particular type andcolor of substrate on which printing is desired. The offset color may bestored in a configuration entry for use whenever printing on thissubstrate type. In Step 302, initiate a print job that includes printingan image on a colored substrate, the corresponding color offsets ofwhich were determined in Step 301. In Step 303, the printer prints awhite layer that includes an amount of colored ink determined by lookingof the colored substrate offset color values in the white balanceprofile, and adding a corresponding amount of each offset color.

In an embodiment of the invention, a pre-setting look-up table or otherprofile storage mechanism may be used to store characterizations forvarious media in a media database. The media database may store a mediaidentifier that uniquely identifies the media type and color. The colorof each media may be explicitly identified or may simply bedistinguished from the other colors of that media type in the database.That is, there may be multiple identified media of the same type havingdifferent colors, and each may be assigned a different identifier. Thus,each unique substrate identifier unambiguously identifies an amount ofink to add to the white layer to compensate for the color of thesubstrate. Thus, the predetermined colors and color amounts that are tobe added to the white layer for such media to counteract certain popularmedium colors may be stored as configuration information in associationwith the substrate identifier. In this embodiment of the invention, suchprofile information may be accessed by software within the printer orprinter driver, for example via a drop-down menu in the printer's userinterface. For example, the user may choose to print on a red medium forwhich a counteracting color may be added to the white layer to yield aperceptibly neutral “white” layer (i.e. neutral layer may be a shade ofgray). In this case, the printer software, operating in the background,may retrieve previously stored information for counteracting the cast ofsuch a medium to establish a correct white balance when printing thewhite layer.

Creating a White Balance Profile Different ink sets react to mixingcolors differently. Thus, each distinct ink set may have a distinctwhite balance profile. The white balance profile may associate a varietyof Red-Green-Blue (RGB) values with a corresponding mixture of Cyan,Magenta, and Yellow (CMY). Alternatively, the white balance profile mayassociate CMY values of a desired color with the percentage color, whichwhen requested of the printer, prints the desired color. To determinethe desired CMY values, an instrument such as a spectrophotometer may beused to measure the RGB values of a color sample, then convert the RBGvalues to CMY values for storing in the profile.

FIG. 2 is a flow diagram that shows how to automatically create a whitebalance profile for a particular ink type. In Step 400, using thedesired ink type, blocks of white are printed, each block printed with acolor comprised of white ink mixed with incremental percentages of theCMY colors. In an embodiment, the range of percentages for eachindividual color may range from 1% to 10%. In an embodiment, the whiteblocks are printed in 0.5% increments. In another embodiment, anincrement of about 0.4% may be used. For example, a set of blocks may beprinted using the ink type mixed as follows:

-   -   Blocks of cyan: {0% cyan, 0.39% cyan, 0.78% cyan, 1.18% cyan,        1.67% cyan, 1.96% cyan, 2.35% cyan, 2.75% cyan, 3.14% cyan,        3.53% cyan, 3.92% cyan}    -   Blocks of magenta: {0% magenta, 0.39% magenta, 0.78% magenta,        1.18% magenta, 1.67% magenta, 1.96% magenta, 2.35% magenta,        2.75% magenta, 3.14% magenta, 3.53% magenta, 3.92% magenta}    -   Blocks of yellow: {0% yellow, 0.39% yellow, 0.78% yellow, 1.18%        yellow, 1.67% yellow, 1.96% yellow, 2.35% yellow, 2.75% yellow,        3.14% yellow, 3.53% yellow, 3.92% yellow}

In an embodiment, blocks may also be printed with combinations of thesecolors. The selection of these percentages corresponds to distinct RGBvalues that are relative to 255. Thus, the difference between an RGBvalue of 233 and 234 is 1/255 or 0.39%. However, any sufficiently smallincrement may be used.

In Step 410, the color density of each printed block may be measured andthe measurement stored in association with the percentage of color usedto print the measured block. An instrument such as a densitometer,spectrophotometer, or a camera may be used to measure the color of eachof the blocks on an RGB scale. A densitometer is a device that measuresthe degree of darkness, i.e. the optical density, of a photographic orsemitransparent material or of a reflecting surface. The densitometer isbasically a light source aimed at a photoelectric cell. It determinesthe density of a sample placed between the light source and thephotoelectric cell from differences in the readings. A densitometer mayread color from black (none) to white (all). Densitometers may readthree colors at a time red, green and blue. Three densitometers may beused inside each unit with a filter for each different color.

Spectrophotometry is the quantitative measurement of the reflection ortransmission properties of a material as a function of wavelength. It ismore specific than the general term electromagnetic spectroscopy in thatspectrophotometry deals with visible light, near-ultraviolet, andnear-infrared, but does not cover time-resolved spectroscopictechniques. Spectrophotometry involves the use of a spectrophotometer,which is a photometer that can measure intensity as a function of thelight source wavelength. Important features of spectrophotometers arespectral bandwidth and linear range of absorption or reflectancemeasurement.

A spectrophotometer and a densitometer are similar devices. Adensitometer is used to measure intensity of a single wavelength. Betterdevices allow a few discrete wavelengths such as the typical red, greenand blue (RGB). A spectrophotometer is a more sophisticated piece ofequipment than a densitometer. A spectrophotometer uses a prism and anarray of sensors to measure the density of all the colors at once:red-orange-yellow-green-blue-purple and hundreds in between. However, aspectrophotometer costs about the same as a densitometer, so it iscommon to use a spectrophotometer to simply read red-green-blue.

A camera may be used to determine an RGB value for an area ofperceptibly uniform color. The camera may measure the RGB values ofvarious pixels within the area and average the RGB values of the pixelsto derive an average RGB value for the area. A camera may be used tomeasure RGB values instead of using dedicated densitometers. Forexample, a camera described in issued U.S. Pat. No. 8,459,773 may beused to measure RGB values.

In an embodiment of the invention, a spectrophotometer may be integratedinto the printer; however, a densitometer or camera may alternatively beused. Furthermore, those skilled in the art will appreciate that othertechniques may be used to measure the white layer to determine if awhite balance correction is required in accordance with the inventionherein.

FIG. 3 is an example table of measured and recorded RGB values (on ascale from 0 to 255) for each block that was printed. The columns of thetable represent the percentage of cyan, magenta, or yellow that theprinter was requested to print for each block. The values in the cyanrows include the red value, the green value, and the blue value thatwere recorded after measuring the RGB values for a printed block ofcyan. For example, the Cr row contains the measured red value whenmeasuring a block of cyan that was printed with an intensitycorresponding to the column value. For example, the Cr value in the0.78% value column is 238. The Cg row contains the measured green valuewhen measuring a block of cyan for the various intensities. “Mg”represents the green measurement of the magenta printed blocks, and “Yb”represents the blue measurement of the yellow printed blocks.

The measured RGB values seen in the table of FIG. 3 are used to derivethe values in the table in FIG. 4. The values in FIG. 4 are percentagesof cyan, magenta, and yellow, rather than RGB values. The columnheadings for FIG. 3 and FIG. 4 are the same, but 3 RGB values are usedto determine the single entry in a row of cyan, magenta, or yellow. Forexample, in the column 0.78% of FIG. 3, there are 3 values for cyan:red=238, green=240, and blue=244. RGB values may be converted to CMYvalues due to current technology optical color recognition technologyreturning RGB values and color printers using a CMYK color model.If/when CMY color measurement technology becomes practical to use, thetable shown in FIG. 4 may be constructed without needing FIG. 3.Alternatively, an RGB-based printer may use FIG. 3 as the white balanceprofile, because there will be no need to convert to CMY.

In Step 420, the three RGB values are used to determine thecorresponding C, M, Y values for the rows in FIG. 4. The color wheel inFIG. 5 illustrates the inverse color as being located directly acrossthe circle. For example, magenta and green are directly across from eachother, and thus, magenta is the inverse color to green. Likewise, blueand yellow are inverse colors and red and cyan are inverse colors. Forideal true colors, a formula to convert RGB values to a percentage ofcyan would simply be 1−(red value/255). That is, red is directlymeasured, and cyan, the inverse of red, may be determined by subtractingthe red measured percentage from 100%. Other formulae may be used toreflect an imperfect world. For example, a formula used to compute thevalues in FIG. 4 is:

Cyan %=((Blue value+Green value)/2−Red value)/255

Magenta %=((Red value+Blue value)/2−Green value)/255

Yellow %=((Red value+Green value)/2−Blue value)/255

To determine a cyan percentage from our example {238, 240, 244}:

Cyan %=((244+240)/2−238)/255

(484/2−238)/255

(242−238)/255

4/255=1.57%

In Step 430, the converted CMY values for each measured block may bestored in a white balance profile. The profile is expressed as a tablein this example. However, the profile may be represented as multiplelines of comma separated values.

In an embodiment, a printer manufacturer may create a white balanceprofile for each ink set supported by the printer, and the white balanceprofiles may be stored in a media database that is shipped with theprinter. In another embodiment, an ink manufacturer may create a whitebalance profile for their ink on a particular printer and the profilemay be downloaded into the printer over the Internet.

Printing an Image on a Colored Background Using a Separate White Layer

When printing an image on a colored background, a two-step process maybe used. The first step is to print a layer of white onto the coloredbackground where the image will eventually be printed, and the secondstep is to print the image on top of the white layer. However, if thewhite layer does not completely cover the colored background, a colorneeds to be to mixed into the white layer so that the white layerappears neutral.

In certain high end printers, the process of determining which colors tomix may be performed automatically by the printer. FIG. 6 is a flowdiagram that shows how to automatically configure a printer for whitebalancing a background layer of white on a colored medium. In Step 500,a test block of white, such as would be printed as the white layer, isprinted on the colored background. In Step 510, a spectrophotometer orother similar device in the printer scans a portion of the test whiteblock to determine the RGB values of the block. For example, printing atest white block on a blue background may be measured as having thefollowing RGB readings values {R=238, G=238, B=253}. The RGB value forwhite is {255,255,255} so the example measured value is close to white,but may have a bluish tinge.

In Step 520, the color closest to a neutral color is determined for themeasured white layer. The neutral color most closely corresponding tothe measured RGB value has red, green, and blue values equal to thelowest value across the red, green, and blue measurements. The lowest ofthe RGB values, which is 238 in our example, is subtracted from each ofthe RGB values, resulting in {R=0, G=0, B=15}. These resulting RGBvalues represent the difference from the nearest achievable neutralcolor. The measured white layer on the colored medium is measured at15/255 or 5.88%.

Knowing a color's measured value allows determining how to white balancethat color. For example, if a color is created by mixing 1% red withwhite, then adding 1% of red's inverse color (i.e. cyan) may restore thecolor to white (or other neutral color). If a color is measured ascomprising a 2% blue value, then adding 2% yellow may restore the colorto neutral. In general, each of the colors CMY has an opposite/inversecolor that is added to the mixture in the same percentage. A neutralcolor such as white or gray have all three RGB values equal to eachother, such as black (0, 0, 0), white (255,255,255), and at least 254shades of gray, e.g. (138, 138, 138). The human eye perceives thedifferences in density of the red, green, and blue color at least asmuch, if not more so, as the absolute density of each color. Thus, onlythe percentage difference in density needs to be preserved to have thesame effect. To make the white layer appear neural, the bluish tinge maybe corrected by adding 5.88% of blue's inverse color, yellow, to thewhite layer when printing on this colored medium. Thus, a small amountof yellow may be added to the example test white block to make the whitelayer appear less blue and more neutral.

In Step 530, the offsets may be stored in a configuration entry for theparticular colored material for future use. This configuration entry maybe selected in the future for use when white balancing the printer for aparticular print job to be printed on the same colored material usingthe same type ink. Thus, the use of a spectrophotometer may only beneeded the first time printing on a particular colored material, and theresults saved for future use.

For printers not including a spectrophotometer or other opticalmeasuring device, an alternate manual process may be used to configurethe printer white balance for a particular colored background and inkset. FIG. 7 is a flow diagram that shows how to manually configure aprinter for white balancing a background layer of white on a coloredmedium. The first step, Step 600, is the same as Step 500 in FIG. 6. Atest block of white is printed on the colored background. However, inStep 610, instead of using a spectrophotometer, the user visuallyinspects the test white block to determine whether it is neutral enoughor whether white balancing is needed. If the block is not neutralenough, then in Step 620, a user may use a slider user interface such asshown in FIG. 8 to specify how to adjust the printer colors of magenta,cyan, and yellow.

FIG. 8 shows a user interface which may be used to manually adjust whitebalance when printing an image on a colored medium according to theinvention. In FIG. 8, user controls are provided to allow individualprint ink colors (CMY) to be adjusted from 0.001-10% of the base whiteink layer that is to be applied to the medium. In this embodiment, theprinter automatically prefers light inks over dark inks to reducegraininess in the white layer. The white balance slider user interfacemay be run on a computer that is directly connected to the printer or ona network where the printer resides. In Step 630, the offsets selectedon the white balance slider are used to configure the printer, and inStep 640, the user prints another test white block using the new printerconfiguration. The user inspects the new test white block and continuesin this trial and error fashion until the resulting test white block inStep 610 appears neutral enough. At Step 640, the offset values used toconfigure the printer that resulted in a white block being neutralenough may be stored in the media database in association with thecolored media and ink set.

Using the Printer Configuration for White Balancing

When a user wants to print an image on a colored material for whichoffsets have been stored in the media database, the printerconfiguration process may proceed as illustrated in FIG. 9. FIG. 9 is aflow diagram that shows how to print an image on a colored medium. Theconfiguration dialog may include selecting the ink set type andidentifying the colored material for which offsets have been calibrated(in Step 700). Before the image is printed on the medium, the offsetsfor that colored medium are retrieved from the media database (Step710). For example, continuing with the above example, the user mayconfigure the printer by providing the identifier for the blue substratetype for which offsets were stored in a configuration entry of the mediadatabase. The offset color value(s) are each found in the correspondingrow of the white balance profile of FIG. 4 to determine how much ofcyan, magenta, and yellow to request the printer to use when printingthe white layer. The desired percentage of yellow ink stored in theconfiguration entry is 5.88%. The value 5.88% is looked up in the yellowrow of the white balance profile. The value 5.88% is in between columns1.57% and 1.96%, so the printer would be requested to print a percentageof yellow that is between 1.57% and 1.96%, to correct the white layer.In an embodiment, more than one of magenta, cyan, and yellow may need tobe added to the white layer to correct for the colored substrate. Inthat case, each of the added colors may be independently looked up inFIG. 4 to find the percentage of that color to request of the printer.

The information retrieved from the white balance profile may be used toconfigure the inks to use for printing the white balance layer (Step720). When the white layer is printed, the white layer will reflect theoffsets known to counteract the underlying media color.

Other Embodiments

In an embodiment of the invention that provides a media database for thevarious types of media that are to be used with a printer, a descriptionof the medium may be provided, and the printer software may warn theuser in certain instances, e.g. using flood white on a particularsubstrate, may not result in a true white background. In this example,the warning to the user may offer the user the option to neutralize theeffect of the colored medium on the white layer by selecting theaddition of a colored ink to add to the white layer, as discussed above.The user could choose to select the addition of color to the white layeror could print without adding color to the white layer.

In another embodiment of the invention, a facility built into theprinter, in a separate tool, or with a cell phone camera having aninstalled app allows the user to take a picture or use a sensor to lookat the medium and then, based on picture, the user can select a correctprofile in the printer for that medium, and the profile is then appliedto the white layer automatically.

In another embodiment of the invention, the density of a printed imagemay be measured for consistency over the course of an extended printrun, for example at a print shop from the beginning of the day to theend of the day. Periodic measurement of white layer color can be taken,and used to maintain a consistent print quality. Thus, if values for awhite layer applied to a medium vary from neutral, the system mayautomatically adjust the profile to account for such variations; or, ifthe medium itself varies from package to package, then adjustments canbe made to the amount of color to be added to the white layer tomaintain a neutral white balance. In this later embodiment of theinvention, spot checks may be performed on the medium and adjustmentsmade to the white layer profile to account for variations in the mediumfrom lot to lot.

Computer Implementation

FIG. 10 is a block schematic diagram that depicts a machine in theexemplary form of a computer system 1600 within which a set ofinstructions for causing the machine to perform any of the hereindisclosed methodologies may be executed. In alternative embodiments, themachine may comprise or include a network router, a network switch, anetwork bridge, personal digital assistant (PDA), a cellular telephone,a Web appliance or any machine capable of executing or transmitting asequence of instructions that specify actions to be taken.

The computer system 1600 includes a processor 1602, a main memory 1604and a static memory 1606, which communicate with each other via a bus1608. The computer system 1600 may further include a display unit 1610,for example, a liquid crystal display (LCD) or a cathode ray tube (CRT).The computer system 1600 also includes an alphanumeric input device1612, for example, a keyboard; a cursor control device 1614, forexample, a mouse; a disk drive unit 1616, a signal generation device1618, for example, a speaker, and a network interface device 1628.

The disk drive unit 1616 includes a machine-readable medium 1624 onwhich is stored a set of executable instructions, i.e., software, 1626embodying any one, or all, of the methodologies described herein below.The software 1626 is also shown to reside, completely or at leastpartially, within the main memory 1604 and/or within the processor 1602.The software 1626 may further be transmitted or received over a network1630 by means of a network interface device 1628.

In contrast to the system 1600 discussed above, a different embodimentuses logic circuitry instead of computer-executed instructions toimplement processing entities. Depending upon the particularrequirements of the application in the areas of speed, expense, toolingcosts, and the like, this logic may be implemented by constructing anapplication-specific integrated circuit (ASIC) having thousands of tinyintegrated transistors. Such an ASIC may be implemented with CMOS(complementary metal oxide semiconductor), TTL (transistor-transistorlogic), VLSI (very large systems integration), or another suitableconstruction. Other alternatives include a digital signal processingchip (DSP), discrete circuitry (such as resistors, capacitors, diodes,inductors, and transistors), field programmable gate array (FPGA),programmable logic array (PLA), programmable logic device (PLD), and thelike.

It is to be understood that embodiments may be used as or to supportsoftware programs or software modules executed upon some form ofprocessing core (such as the CPU of a computer) or otherwise implementedor realized upon or within a machine or computer readable medium. Amachine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine, e.g., acomputer. For example, a machine readable medium includes read-onlymemory (ROM); random access memory (RAM); magnetic disk storage media;optical storage media; flash memory devices; electrical, optical,acoustical or other form of propagated signals, for example, carrierwaves, infrared signals, digital signals, etc.; or any other type ofmedia suitable for storing or transmitting information.

Although the invention is described herein with reference to thepreferred embodiment, one skilled in the art will readily appreciatethat other applications may be substituted for those set forth hereinwithout departing from the spirit and scope of the present invention.Accordingly, the invention should only be limited by the claims includedbelow.

1. A method for printing an image on a substrate, the substrate having aparticular color, the method comprising: receiving from a user anindication of a substrate type on which to print an image, theindication associated with the particular color of the substrate type;retrieving from a configuration file, based at least on the particularcolor of the substrate type, a first offset color value for a firstoffset color; wherein a color value indicates an amount of each of thecolors of ink used by the printer; in a first pass, printing on asubstrate of the substrate type a first layer of white ink mixed with anamount of each colored ink indicated by the first offset color value;wherein the printed first layer of mixed ink appears as a neutral color,so that the particular color of the substrate is not visible; in asecond pass, printing the image on top of the first layer; wherein thecolors of the image are not modified based on the particular color ofthe substrate.
 2. The method of claim 1, further comprising adding anentry to the configuration file for a substrate type of the particularcolor, further comprising: printing a layer of white ink on a test pieceof substrate of the substrate type; determining that the layer of whiteappears as comprising a second color hue; measuring the second color hueto determine a second color hue value; determining a third offset colorvalue of a third offset color based on the second color hue value,wherein the third offset color value indicates an amount of each coloredink to mix with the white ink; storing in the entry of the configurationfile the third offset color value in association with the substratetype.
 3. The method of claim 2, wherein the second color hue is measuredby a spectrophotometer, a densitometer, or a camera to determine thesecond color hue value.
 4. The method of claim 2, wherein the secondcolor hue value comprises a red, green, and blue (RGB) value.
 5. Themethod of claim 2, wherein determining the third offset color valuecomprises determining an inverse of the second color hue value;
 6. Themethod of claim 2, wherein the third offset color value is stored in theconfiguration file entry as an RGB value.
 7. The method of claim 2,wherein the third offset color value is stored in the configuration fileentry as an cyan, magenta, yellow (CMY) value.
 8. The method of claim 1,wherein determining the amount of each colored ink to mix with white inkto form a neutral layer further comprises: looking up a second offsetcolor value in a white balance profile based on the first offset colorvalue, wherein the white balance profile was previously created for thetype of ink being used by the printer; determining to use the amount ofone or more colored inks indicated by the second offset color value. 9.A printer system comprising: a processor; a printer mechanism that jetsink onto a colored substrate to produce an image; a storage devicestoring one or more configuration files; wherein the printer mechanismis configured to print a first layer of white ink on the coloredsubstrate and a second layer comprising the image on top of the firstlayer; the storage device configured to retrieve from a configurationfile a color value based on an indication of the substrate type; whereinthe color value indicates an amount of each colored ink used by theprinter; and the printer mechanism configured to mix the amount of eachcolored ink is indicated by the retrieved color value with the white inkwhen printing the first layer.
 10. The printer system of claim 9,further comprising: an optical measuring device that measures a regionof color of the white layer printed on the colored substrate; theprocessor configured to determine, based on a measurement obtained fromthe optical measuring device, a measured color value for the region ofcolor; the processor configured to determine an offset color value of anoffset color, wherein the offset color value indicates an amount of eachcolored ink with which to mix with white ink to mask the color of thesubstrate when printing the first layer on the colored substrate; andthe storage device configured to store in a configuration file themeasured color value in association with the substrate type.
 11. Theprinter system of claim 9, further comprising: a user interface forreceiving from a user an indication of a substrate type on which toprint an image; wherein the substrate type indicates the color of thesubstrate.
 12. The printer system of claim 9, further comprising: a userinterface for receiving from a user a color value for each of at leastone of a plurality of colors; the user interface comprising: aninteractive element for each of the at least one of a plurality ofcolors, the interactive element receiving from the user a color valuecorresponding to said each color; a trigger element for causing theprinter to print a sample block color by mixing white ink with specifiedamounts of colored inks indicated by said each color value; an inputelement that allows the user, responsive to visually inspecting thesample block color, to select one or more color values to store in aconfiguration entry in association with the substrate type and color.13. The printer system of claim 12, further comprising: the storagedevice further configured to store, in association with a mediaidentifier, the one or more color values received from the user.